Method for protecting pin code on android platform

A method for protecting a personal identification number (PIN code) on an Android platform, comprising:

• step S1) invoking, by a Java layer, a C layer via a Java native interface (JNI), and introducing a start event to the C layer;
• step S2) invoking, by the C layer, the Java layer via the JNI after the start event is received by the C layer;
• step S3) generating, by the Java layer, a password-storage-class-instance, and returning a handle of the password-storage-class-instance to the C layer;
• step S4) invoking, by the C layer, the Java layer via the JNI after the handle of the password-storage-class-instance is received by the C layer;
• step S5) monitoring, by the Java layer, input from a user;
• if it is monitored that PIN code data is input by the user, storing the PIN code data currently input by the user into a data memory of the password-storage-class-instance, and updating a storage location identification in the password-storage-class-instance, invoking the C layer via the JNI, introducing an encrypting event to the C layer, and executing step S6;
• if it is monitored that confirmation information is input by the user, invoking the C layer via the JNI, introducing a confirming event to the C layer, and executing step S7;
• step S6) accessing, by the C layer, the password-storage-class-instance via the handle of the password-storage-class-instance, looking up the PIN code data currently input by the user according to the storage location identification in the password-storage-class-instance, encrypting the found PIN code data currently input by the user to obtain current encrypted data, storing the current encrypted data into the data memory of the password-storage-class-instance, deleting the found PIN code data currently input by the user, and returning to the step S5;
• step S7) accessing, by the C layer, the password-storage-class-instance according to the handle of the password-storage-class-instance, and decrypting all of the encrypted data stored in the data memory of the password-storage-class-instance to obtain a PIN code input by the user.